Causes and solutions of motor noise or abnormal sound fault
Cause 1: The motor bearing clearance is large.
Solution: Replace the bearing.
Reason 2: the motor rotor sweeps the hall.
Treatment: Repair the stator and rotor again.
Reason three: the magnetic steel is loose.
Treatment method: Re-bonding magnetic steel.
Reason 4: The motor body is skewed.
Treatment: readjust your body.
Reason 5: the surface of the motor steering gear is oxidized and ablated, the oil stain is uneven and the commutator is loose.
Treatment method: clean the commutator surface or weld firmly.
Reason 6: The carbon brush is loose and the carbon brush holder is incorrect.
Treatment method: adjustment
First of all, make sure that the quality of the motor itself is ok.
Secondly, when the inverter controls the motor, it is normal for the motor to howl and vibrate, because the inverter outputs PWM wave or s PWM wave instead of sine wave.
Two solutions, one is to adjust the carrier frequency of the inverter and improve the carrier frequency; Another method is to install an inverter output filter or reactor at the inverter output.
First, the inverter is used to control the variable frequency motor. Vibration is usually caused by the pulsating torque of the motor and the vibration of the mechanical system, especially when the pulsating torque coincides with the vibration of the mechanical system.
This kind of noise is usually divided into inverter noise and motor noise, and different treatment measures should be taken according to different installation sites: in the debugging process of inverter, the pulse torque component should be reduced as much as possible on the premise of ensuring control accuracy; Debug and confirm the mechanical vibration points, and use the frequency shielding function of the inverter to exclude these vibration points from the operating range; Because the noise of the inverter is mainly generated by the reactor of the cooling fan, low-noise devices are selected; A reasonable AC reactor is set between the motor and the frequency converter to reduce the higher harmonics caused by PWM modulation. This is the vibration generated by higher harmonics on the iron core, because the frequency is within the frequency range that people can feel, so they can be heard. The carrier frequency can be increased, and then the inverter output filter and output reactor are connected at the output end of the inverter, so that the output current is close to sine wave and the higher harmonic component is reduced, and this noise will be greatly reduced. These noises are caused by a large number of high-frequency harmonics in the power supply output by the frequency converter. In this case, customers are generally advised to install an inverter output filter at the output end of the inverter, which can improve the waveform at the output end of the inverter and reduce its high-frequency harmonic components, and the effect is very obvious.
Second, use frequency converter to eliminate the noise generated by motor;
The carrier frequency of the inverter can be changed, but I don't recommend that you change this parameter at will. In order to reduce noise, the carrier frequency of the inverter can be set higher, but it will bring some problems. If the carrier frequency is set too high, it will cause interference to other equipment, especially when PLC communication mode is adopted. Therefore, the carrier frequency should be set according to the actual situation. If you are not an experienced engineer, it is recommended not to change the carrier frequency parameter. The carrier frequency parameter of MM440 inverter is P 1800.
There are two reasons for motor noise: mechanical and electrical.
1, mechanical aspects, such as damage or scratch of motor cooling fan, unstable motor fixing, etc. This situation is easy to handle, as long as the noise source can be found, it is generally easy to handle.
2. Electrical aspects
(1) The carrier frequency of the inverter is set too low. You can set the carrier frequency higher, but it will bring some problems. If the carrier frequency is adjusted too high, it will cause interference to other equipment, especially when plc communication mode is adopted. Therefore, the carrier frequency should be set according to the actual situation.
(2) Motor vibration. Sometimes, when the motor is running, it will produce mechanical vibration in a certain frequency band. At this time, the frequency hopping setting mode of frequency converter can be used. Generally, frequency converters have "frequency hopping" settings to set the frequency of motor vibration. When the inverter runs in this frequency band, it will skip this frequency to avoid motor vibration.
(3) The load capacity of the motor is reduced. Sometimes the motor is used for a long time, or the quality of the motor is not good, and the load capacity will be reduced. The motor noise here will be louder than usual.
(4) The higher harmonics of the frequency converter are large. When the higher harmonic component of the inverter is large, it is easy to cause the motor vibration to increase, the speed jitter to be unstable, and the motor noise to increase. Input and output reactors have been added here.
Third, the output cable contains considerable higher harmonic voltage and current, which distorts the input voltage of the motor and further increases the higher harmonic of the electromotive force of the stator and rotor, resulting in serious distortion of the phase electromotive force, leading to serious heating of the motor coil, insulation aging and even breakdown; In addition, due to the additional torque generated by the harmonic magnetic field, the motor produces obvious vibration and sharp noise. Higher harmonics will greatly shorten the mechanical life and insulation life of the motor.
The harmonic output by inverter is the main reason for high frequency howling of motor. When the modulation pulse frequency of inverter power switch is increased, the output current is closer to sine wave, and the howling frequency is increased beyond the range of audible sound waves, which will greatly reduce the howling. However, when the switching frequency of IGBT is too high, the loss on IGBT will increase, so it is necessary to reduce the capacity of inverter. Generally, when the switching frequency of IGBT is 4Khz, if you hear howling, it is suggested to increase the switching frequency of IGBT appropriately. At present, the howling of frequency conversion motor in operation often gives people an illusion that it is caused by frequency modulation of frequency converter, but it is not necessarily so. We should confirm the source of the howling before dealing with it.
Step 1, the frequency converter adopts V/F control to make the motor run at high speed;
Step 2, then operate the OFF2 of the frequency converter to stop automatically;
Step 3, it is judged that the motor decreases with the speed during free parking. If howling or vibration still exists and there is no frequency conversion control, it is a production problem of the motor, and there are * * * vibration points in the operation of mechanical transmission. Explain that it is a mechanical manufacturing problem, not an electrical control problem. If the motor runs smoothly and there is no howling during free parking, it is a control problem of the inverter, which can be solved by adjusting the control parameters of the inverter. Among them, it is very important to calculate the dynamic and static mathematical models of the motor with frequency converter. If the mathematical model established by the inverter is accurate, the operation quality will be good. The electromagnetic noise of the control motor is completely acceptable. There is no doubt about it.
Fourth, how to solve the problems of fever, vibration and noise after motor frequency converter speed regulation.
In our daily use, the frequency converter will produce noise and vibration after speed regulation. This situation is due to the influence of higher harmonic components in the output waveform of frequency converter. With the change of motor operating frequency, the fundamental component and higher harmonic component change in a large range, which is easy to cause resonance with various parts of the motor. The harmonics of the frequency converter may also affect other electronic devices. When the motor is driven by frequency converter, the output voltage and current contain higher harmonic components, and the higher harmonic magnetic flux in the air gap increases, so the noise increases. The characteristic of electromagnetic noise is that the low harmonic component in the inverter output resonates with the mechanical natural frequency of the rotor, so the noise near the natural frequency of the rotor increases. The harmonic components in the output of the frequency converter resonate with the bearing frame of the iron core shell. And the noise near the corresponding natural frequencies of these components increases. The harsh noise generated when the inverter drives the motor is related to the switching frequency of PWM control, especially in the low frequency region. The suppression method is to set an AC reactor at the output side of the frequency converter. If there is electromagnetic torque margin, U/F can be set smaller. When the noise of special motor is serious in lower frequency band, it is necessary to check the resonance with the natural frequency of shafting (including load). When the frequency converter works, the magnetic field generated by the higher harmonics in the output waveform generates electromagnetic vibration force on many mechanical parts, and the frequency of the vibration force can always approach or coincide with the natural frequency of these mechanical parts, thus generating * * * vibration. The higher harmonics that have great influence on vibration are mainly lower harmonics, which have great influence in PAM mode and square wave PWM mode. However, when sine wave PWM mode is adopted, the low-order harmonic component is small and the influence becomes smaller. The way to reduce or eliminate vibration is to set an AC reactor at the output side of the frequency converter to absorb the higher harmonic current component in the output current of the frequency converter. When PAM or square wave PWM inverter is used, sine wave PWM inverter can be used to reduce pulsating torque. The causes of motor vibration can be divided into electromagnetic reasons and mechanical reasons.
1) The vibration caused by electromagnetic causes shows that the resonance between the low-order harmonic component and the rotor increases the vibration component near the natural frequency. Vibration occurs due to the influence of pulsating torque generated by harmonics, especially when the frequency of pulsating torque is consistent with the torsional natural frequency of shafting composed of motor rotor and load.
2) The vibration caused by mechanical reasons is as follows: when the motor shaft is suspended and the natural frequency of the shafting is reduced, if the motor runs at high speed and the full rotation frequency is close to the natural frequency of the shafting, the vibration will be aggravated. Residual unbalance of rotor
The centrifugal force increases in direct proportion to the quadratic power of the rotational speed, so the vibration increases when the motor is driven by the frequency converter at high speed. Frequency converter is an electronic device, so the temperature has a great influence on its life. Generally, the ambient temperature of frequency converter is required to be-10~50℃. If the working temperature of the inverter can be reduced, the service life of the inverter will be prolonged and the performance will be stable. The heating of frequency converter is caused by internal loss, mainly the main circuit, accounting for about 98% of the total loss, and the control circuit accounts for 2%. In order to ensure the normal and reliable operation of the inverter, the inverter must be cooled. The main methods are:
1) adopt a fan to dissipate heat: the built-in fan of the inverter can take away the heat inside the inverter box.
2) Adopt an independent inverter room with air conditioner installed indoors, and keep the temperature at 15~20℃. The above-mentioned frequency converter heating refers to the loss caused by the normal operation of the frequency converter within the rated range and the loss caused by the abnormal operation of the frequency converter (such as overcurrent, overvoltage, overload, etc.). ) must be avoided by normal selection.